1. Field of the Invention
The present invention generally relates to a backlight module, more particularly to a backlight module having a palette device.
2. Description of the Prior Art
A general display with the feature of autoluminescence as an LCD may need a backlight source for displaying images. For several prior backlight technologies, the backlight module with the feature of inputting light from a side end thereof may be more demanded to the needs of slim product. Such technologies are being widely applied to the screen of a laptop computer and an LCD.
With references to FIG. 1 and FIG. 2, which illustrates a schematic view of a prior backlight module and a schematic view of a light-guide plate and an LED bar of the prior backlight module. As shown in the figures, a backlight module 10 includes a light-guide plate 11, an LED bar 12, a reflector 13, and a plurality of optical films 14. The light-guide plate 11 has a side end 111 and an emergent surface 112. The LED bar 12 is disposed at the side end 111 of the light-guide plate 11. The plurality of optical films 14 are disposed on the emergent surface 112 of the light-guide plate 11. The reflector 13 is disposed on the bottom of the light-guide plate 11, wherein the bottom is corresponding to the emergent surface 112.
A plurality of white light LEDs 121 are disposed at the LED bar 12 and corresponding to the side end 111 of the light-guide plate 11 in order to emit a linear light. The linear light from the LED bar 12 passes through the side end 111 of the light-guide plate 11 and then into the light-guide plate 11. The incident linear light from the LED bar 12 is totally reflected within the light-guide plate 11 due to a total reflection interface in the light-guide plate 11. Continuously, the light is output from the emergent surface 112 and passes through the plurality of optical films 14 to an LCD not shown in the figures.
The area of the emergent surface 112 is almost the same as the display, that is, the backlight module 10 is able to provide a uniform area light to the display.
Further, the plurality of optical films 14 have at least one brightness enhancement film and at least one diffuser in order to strengthen the light quality provided by the backlight module. The reflector 13 below the light-guide plate 11 is to avoid the incident light emitting downwardly and promote the usage rate of light.
As aforesaid, the LED bar 12 emits white light by means of the white LEDs 121. Generally speaking, the white LED 121 emits a white light by way of a blue LED motivating yellow florescence, that is, a florescent white light LED. The color of the white light LED is closer to the blue color tone and short of red color tone. Thus, the color of the LCD is a little bit ashy.
Other factors as the changeable wavelengths of the blue light LED, the changeable contents of the florescence and the differences between the thicknesses of the light-guide plates are the key roles to cause the white light closer to the blue color tone. In another word, the differences between different color tones make error distributions in color coordinates (x, y). Hence, QC is hardly made.
A distribution range of the white light LED in color coordinates (x, y) is around 0.28 to 0.32. If under the condition of 6500K (D65) of a color temperature, the color coordinates is (0.31, 0.32). The variety (Δx, Δy) must be controlled within 0.005 so as to control the color coordinates in a better range.
Presently the distribution range is very broad, and applicative LEDs must be filtered by way of color bin sorting. The only consideration is that the sorted categories may be hundreds so as to cause the problems of overstock, oversorting and labor cost. Besides, the color coordinates of some light from some LEDs are too small so as to cause a condition of hard usage and that the color tone is closer to ashy, and then a defect rate is highly increased.
As a conclusion, how to make the color tone of a backlight module agree with the needs of a display in order to represent the true colors of images will be the first priority to the persons skilled in the art.